Forming device



Nov. 1, 1966 BROWER ET AL 3,282,077

FORMING DEVICE Filed July 29, 1963 9 5 4 rm .iiiilt: riittiiii. W

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3,232,077 FORMING DEVICE David F. Brewer, San Diego, and Edward A. Day, Ranclio Santa Fe, Calif assignors to General Dynamics Corporation, New York, N.Y., a corporation of Delaware Filed July 29, 1963, Ser. No. 298,111 2 Claims. (CI. 7256) This invention relates to electromagnetic forming apparatus and, more particularly, to devices adapted for use as a component of such apparatus and capable of producing a magnetic field of high flux density.

In recent years, methods and apparatus have been employed for forming materials by employing magnetic fields of high flux density. In accordance with such methods and apparatus, a conductive work piece is positioned adjacent a shaped conductor and a current pulse of high amperage is passed through the conductor so as to set up a magnetic field of high flux density about the conductor. This high density magnetic field, the shape of which is dependent upon the shape of the conductor, induces a current in the conductive work piece, which current is concentrated on the surface of the work piece and is always in such a direction as to tend to exclude the magnetic field from the work piece. The interaction of the magnetic field and the induced current causes a pressure to be applied to the work piece proportional to the energy density of the field. In practice, a magnetic field is created which is sufiiciently intense to cause the work piece to be formed by the resulting pressure.

A principal component of an electromagnetic forming apparatus is, of course, the device by which the required magnetic field is created. conventionally, such a device includes a low resistance conductor formed into a helix, a fiat spiral, a loop, or any other configuration which will produce a concentrated magnetic field of the desired shape. In industrial applications in which the forming apparatus is in essentially continuous use for extended periods of time, the extremely high current pulsed through the conductor causes it to become heated and, because of the heavy insulation surrounding the conductor, this heat is not easily dissipated to the atmosphere.

It has been proposed that a liquid coolant be circulated through a tubular conductor to remove the heat therefrom. In such a proposed arrangement, of course, it is necessary to connect both a high voltage source and a coolant supply to the conductor but, in order to insure the safety of operating personnel, as well as for other practical considerations, it is necessary to maintain the coolant supply system at ground potential.

The present invention is directed to an improved liquid-cooled field-producing device and has for its principal object the provision of such a device which is partic ularly adapted to be connected to a supply of liquid coolant.

Another object of the invention is to provide an improved device of the class described which can be easily and conveniently operated in connection with a coolant supply system maintained at ground potential.

A further object of the invention is to provide an improved field-producing device having a tubular conductor connected to a coolant supply maintained at ground potential.

A still further object of the invention is to provide an improved liquid-cooled device for producing a magnetic field of high flux density, which device can be easily and economically produced.

Other objects and advantages of the invention will become apparent with reference to the following description and the accompanying drawing.

"nited States Patent Patented Nov. 1, I966 ice device shown in FIGURES l and 2.

Very generally, a device 11 illustrated in the drawing and constituting one embodiment of the present invention comprises an elongated current'conducting member 13 formed to provide first and second tubular sections 15 and 17 respectively arranged in side-by-side and generally coextensive relation and interconnected at one of their adjacent ends by an intermediate tubular section 19. The member 13 is thus of a forked or narrow U-shaped configuration and the tubular sections of which it is formed define an elongated conduit 21 reversed upon itself and having both its inlet and its outlet located at ends 16 and 18 of the first and second sections located opposite to the intermediate sections 19. These ends are adapted to be connected to a coolant supply (not shown).

The tubular member 13 is wound upon a core 23, with a contact plate assembly 25 being provided to connect the intermediate section 19 to a source of high electrical potential and with a ground plate assembly 27 being provided to connect the opposite ends of the first and second tubular sections 15 and 17, i.e., the ends connected to the coolant supply, to a source of low or ground potential. When the sections are so connected, a pulse 'of high amperage current fiows through the member 13 in parallel paths defined principally by the first and second sections. However, since the ends of the member which are connected to the coolant supply are also maintained at a low or ground potential, insulation and safety problems which might be caused by entry or exit of the coolant at a point of high electrical potential are eliminated.

More specifically, the current conducting member 13 comprises an elongated tube formed of copper or other material having a high conductance and bent upon itself to provide the previously described first, second, and intermediate sections arranged in a forked or narrow U-shaped configuration. The tube, of course, defines the conduit 21. The first and second sections of the tube are covered with an insulating material. The intermediate section, however, which is in the form of a loop due to the manner in which the tube is bent, is not insulated so as to thereby facilitate an electrical connection between the section 19 and the contact plate assembly 25, soon to be described. The opposite ends 16 and 18 of the first and second sections are also free of insulating material to permit connection of these ends to the ground plate assembly 27, described in detail shortly.

As has already been mentioned, the conducting member 13 may be formed into any of several configurations suitable for use in an electromagnetic forming apparatus. Each of these configurations, however, includes at least one turn or loop so as to concentrate the magnetic field produced by the current pulse passing through the member. In the illustrated embodiment, the conductive member 13 is wound in the form of a helix about the core 23, previously referred to, which is molded of a conductive material such as a beryllium-copper alloy to form a hollow cylinder. During the operation of the device, the field produced by current passing through the conductor induces a current in the outer surface of the core, and a radially extending slot 29 is provided in the core so that the induced current may fiow. from the external surface of the core, along the walls of the slot, to the internal surface of the core. A strip of insulating material 31 such as fiber glass reinforced plastic is disposed within the slot to maintain it at the desired size.

The outer surface of the core 23 is provided with a double helical groove 33 which intimately receives the first and second tubular sections of the member 13, these sections being disposed in side-by-side relation and wound simultaneously upon the core. The adjacent grooves 33 and, hence, the first and second tubular sections, are separated by helical ribs 35 which also surround the core. The disposition of the conductive member 13 within the grooves 33 and flanked by the ribs 35 insures a more uniform distribution of the current in the conductive member and minimizes leakage inductance, resistive losses and forces which would tend to separate the conductive member and core.

The core 23 defines a generally cylindrical internal cavity 37 which is adapted to receive a field-shaping element (not shown). One such an element is disclosed in co-pending application Serial No. 243,010 now Patent No. 3,195,335, assigned to the assignee at the present invention.

The conductive member 13 is wound upon the core 23 from one end of the core toward the other, with the looped intermediate section 19 projecting generally radially from the core adjacent one of the ends thereof, and with the ends 16 and 18 of the first and second tubular sections and 17 projecting generally radially from the core adjacent the other of the ends thereof. The looped intermediate section 19 and the ends 16 and 18 are in general alignment with one another in parallel relation to the longitudinal axis of the core, and are maintained in position relative to the core by a mounting bracket 39, soon to be described. The ends of the first and second tubular sections are offset outwardly to facilitate an attachment thereof to the coolant supply system (not shown).

The current-conducting member 13 wound upon the core 23 is structurally reinforced by insulating and structural material disposed on the outer surface thereof. In the illustrated embodiment, the material is in the form of fiber glass roving 43 which is wrapped around the coiled member 13 and those portions of the core which extend beyond it The plastic-impregnated fiber glass roving is, in turn, covered with a coating 45 of insulating material such as a thermosetting epoxy resin.

To further strengthen the device, as well as to confine the flux produced by the coiled conducting member 13, a hollow cylindrical steel supporting shell 47 surrounds the core 23 and conducting member 13 and has aflixed thereto a radially extending plate 49 which is supported by gussets 51 and provides structural support for the mounting bracket 39. A positioning lug 53 projects from the plate 49 to aid in the clamping of the device 11 to the remainder of the electromagnetic forming apparatus.

The shell 47 is provided with a slot 55 in the vicinity of the radially extending support plate 49 and adjacent one of the edges thereof and receives the outwardly projecting end portions 16 and 18 of the first and second tubular members 15 and 17. A notch 57 extends inwardly from the opposite edge of the shell in the vicinity of the radially extending support plate 49 and receives the outwardly projecting loop-shaped intermediate section 19. These outwardly projecting portions of the conducting member 13 are suitably secured to the plate 49, as will hereinafter be explained.

A pair of flat annular rings 59 and 60 formed of an insulating material such as a thermosetting phenolic resin is secured as by fasteners 61 to each end of the core in overlying relation to the edges of the shell 47. The rings serve to maintain the wound core within the shell. One of the rings 60 is provided with a slightly larger central opening to permit insertion of the field-shaping element, not shown but previously referred to, into the cavity 37 of the core wherein it engages the inner face of the ring 59.

The mounting bracket 39 serves as a means whereby the device 11 may be connected to the remainder of the electromagnetic forming apparatus, and also serves as support for the high voltage contact plate assembly 25, the ground plate assembly 27, the intermediate tubular section 19, and the ends 16 and 18 of the first and second tubular sections 15 and 17. The support plate 49 aflixed to the shell 47 forms the principal structural support for the bracket 39 and has secured to one face thereof, hereinafter referred to as the forward face, an insulating sheet 63 formed, for example, of a thermosetting phcnolic resin. The forward face of the sheet 63 is in turn provided with an additional thin coating 65 of insulation. Disposed adjacent the forward surface of the resin coating is the contact plate assembly, hereinafter described. The contact plate assembly 25 comprises a contact positioner 67, a high voltage contact 69, a cover plate 71, and a lead shield 73. The positioner 67 is in the form of a flat plate formed of an insulating material and having a thickness slightly greater than that of the uninsulated section of the member 19. The positioner plate 67 is provided with an elongated slot 75 extending downwardly at a slight inclination from a central generally circular opening and adapter to receive the looped portion ofthe intermediate section 19, which is thus in contact with the coating 65 of the sheet 63 when disposed Within the slot.

The high voltage contact 69 is in the form of a generally circular plug formed of a conductive material such as brass and provided with a flange 77 at its rearward end, the flange having a thickness slightly less than the thickness of the positioning plate 67 and having a diameter slightly less than that of the generally circular opening of the slot 75. The flanged portion of the plug therefore fits comfortably within the slot 75 and its forward end extends forwardly beyond the forward face of the positioning plate 67.

The rearward surface of the contact plug 69 is provided with a somewhat U-shaped groove 79 which is of a depth slightly greater than the thickness of the looped portion of the intermediate tubular section 19 so as to fully accommodate the said upper portion. Accordingly, both the tubular section 19 and the high voltage contact 69 are disposed within the slot 75, with the section 19 disposed within the groove 79 of the contact 69.

The cover plate 71 is disposed adjacent the forward face of the positioner plate and is formed of a durable insulating material. The plate includes a centrally located generally circular opening 81 through which the forward end portion of the high voltage contact plug projects. The forward face of the cover plate has secured thereto the high voltage lead shield 73, also formed of an insulating material. The plates 67 and 71, and insulating sheet 63 are interconnected within one another and with the support plate 49 of the shell 47 by a pair of threaded fasteners 83.

The rearward face of the support plate 49 has disposed adjacent thereto the ground plate assembly 27 comprising a conductive ground plate 85 having a centrally disposed hole 87 through which the positioning lug 53 of the supporting plate 47 projects. A conductive housing 89 is disposed adjacent the lower edge of the ground plate and surrounds the ends 16 and 18 of the first and second tubular sections 15 and 17 which project through the shell 47. The ends 16 and 18, from which the insulation has been removed are anchored to the rearward wall of the housing and each has secured to its outer end a fitting 91 which facilitates connection of the tubular members to a coolant supply. The ground plate assembly 27 including the ground plate 85, the housing 89, and the fitting 91 are each formed of a current conducting material and are so interconnected that they will be maintained at substantially the same electrically potential.

In the use of the device 11, the device is held within a clamp (not shown) forming part of an electromagnetic forming apparatus, with the ground plate 85 connected to ground potential and with the contact 69 connected to a source of high voltage potential. Accordingly, the ends 16 and 18 of the tubular sections will be maintained at ground potential while the intermediate section 19 is selectively connected to a source of high potential, thus selectively causing a high amperage current pulse to pass through the tubular sections and 17. The fittings 91 are connected to a coolant supply and thus permit a coolant to enter one of the ends 15 and 18 of the member 13 and flow through the conduit 21 in a U-shaped path and out the opposite end. These ends of the tubular sections are maintained at ground potential by the plate 85, and hence, will maintain the coolant supply system at ground potential as Well.

While various structural features of a specific embodiment of the invention have been shown and described, it should be apparent that various modifications might be made therein without departing from the scope of the invention.

Various of the features of the invention are set forth in the following claims.

What is claimed is:

1. In an electromagnetic forming apparatus, a device for producing a magnetic field of high flux density, which device comprises an elongated member formed to provide at least one turn and including means defining a first and a second tubular section disposed in adjacent and generally coextensive relation to each other and interconnected at one of their adjacent ends by means defining an intermediate tubular section, said sections being formed of a current-conducting material and being arranged so as to define an elongated conduit having both its inlet and its outlet located at the end of said member opposite said one end, said conduit being adapted to receive a coolant, a generally cylindrical core formed of current conducting material and having an outer surface provided with a double helical groove, helical ribs separating adjacent grooves, said member being formed into a double helix having adjacent turns formed by each of said first and second tubular sections and wound upon said core with each of said turns disposed within a groove of said core and being spaced an equal distance from the longitudinal axis of said double helical groove, a layer of insulating and structural material disposed on the outer surface of said core and said first and second tubular sections, a continuous, conductive shell surrounding said layer, means for interconnecting the conduit defined by said sections with a source of coolant, and a bracket carried by said shell and projecting therefrom, said bracket supporting said intermediate section and said opposite ends of said first and second tubular sections and including a first contact connected to said intermediate section for effecting an electrical connection between said intermediate section and a source of high electrical potential, and a second contact connected to each of the said opposite ends of said first and second tubular sections for effecting an electrical connection between the said opposite ends and a source of low electrical potential.

2. In an electromagnetic forming apparatus, a device for producing a magnetic field in accordance with claim 1 wherein the bracket comprises a conductive support attached to said shell, insulation disposed on one face of said support and a positioner plate of insulation disposed adjacent said insulation and provided with a slot for receiving said intermediate tubular section, wherein said first contact is a contact plug carried within said slot of said positioner plate and projecting therefrom, said plug including a groove for receiving a portion of said intermediate tubular section, wherein the bracket further comprises a cover plate of insulation disposed adjacent said positioner plate and having a hole therein to receive the projecting portion of said plug, and wherein said second contact is disposed adjacent the uninsulated face of said support.

References Cited by the Examiner UNITED STATES PATENTS 2,075,622 3/ 1937 Nehlsen 72342 3,114,585 12/1963 Brower et al 7256 3,126,937 3/1964 Brower et al 7256 CHARLES W. LANHAM, Primary Examiner.

L. A. LARSON, Assistant Examiner. 

1. IN AN ELECTROMAGNETIC FORMING APPARATUS, A DEVICE FOR PRODUCING A MAGNETIC FIELD OF HIGH FLUX DENSITY, WHICH DEVICE COMPRISES AN ELONGATED MEMBER FORMED TO PROVIDE AT LEAST ONE TURN AND INCLUDING MEANS DEFINING A FIRST AND A SECOND TUBULAR SECTION DISPOSED IN ADJACENT AND GENERALLY COEXTENSIVE RELATION TO EACH OTHER AND INTERCONNECTED AT ONE OF THEIR ADJACENT ENDS BY MEANS DEFINING AN INTERMEDIATE TUBULAR SECTION, SAID SECTIONS BEING FORMED OF A CURRENT-CONDUCTING MATERIAL AND BEING ARRANGED SO AS TO DEFINE AN ELONGATED CONDUIT HAVING BOTH ITS INLET AND ITS OUTLET LOCATED AT THE END OF SAID MEMBER OPPOSITE SAID ONE END, SAID CONDUIT BEING ADAPTED TO RECEIVE A COOLANT, A GENERALLY CYLINDRICAL CORE FORMED OF CURRENT CONDUCTING MATERIAL AND HAVING AN OUTER SURFACE PROVIDED WITH A DOUBLE HELICAL GROOVE, HELICAL RIBS SEPARATING ADJACENT GROOVES, SAID MEMBER BEING FORMED INTO A DOUBLE HELIX HAVING ADJACENT TURNS FORMED BY EACH OF SAID FIRST AND SECOND TUBULAR SECTIONS AND WOUND UPON SAID CORE WITH EACH OF SAID TURNS DISPOSED WITHIN A GROOVE OF SAID CORE AND BEING SPACED AN EQUAL DISTANCE FROM THE LONGITUDINAL AXIS OF SAID DOUBLE HELICAL GROOVE, A LAYER OF INSULATING AND STRUCTURAL MATERIAL DISPOSED ON THE OUTER SURFACE OF SAID CORE AND SAID FIRST AND SECOND TUBULAR SECTIONS, A CONTINUOUS, CONDUCTIVE SHELL SURROUNDING SAID LAYER, MEANS FOR INTERCONNECTING THE CONDUIT DEFINED BY SAID SECTIONS WITH A SOURCE OF COOLANT, AND A BRACKET CARRIED BY SAID SHELL AND PROJECTING THEREFROM, SAID BRACKET SUPPORTING SAID INTERMEDIATE SECTION AND SAID OPPOSITE ENDS OF SAID FIRST AND SECOND TUBULAR SECTIONS AND INCLUDING A FIRST CONTACT CONNECTED TO SAID INTERMEDIATE SECTION FOR EFFECTING AN ELECTRICAL CONNECTION BETWEEN SAID INTERMEDIATE SECTION AND A SOURCE OF HIGH ELECTRICAL POTENTIAL, AND A SECOND CONTACT CONNECTED TO EACH OF THE SAID OPPOSITE ENDS OF SAID FIRST AND SECOND TUBULAR SECTIONS FOR EFFECTING AN ELECTRICAL CONNECTION BETWEEN THE SAID OPPOSITE ENDS AND A SOURCE OF LOW ELECTRICAL POTENTIAL. 